考虑到页面加载速度和页面布局的需要，很多时候要将用户上传的图片进行缩略，下面这个函数分享出来，希望对大家有用。
它支持gif、jpg、png和bmp几种图片格式，不过bmp图像需要ImageCreateFromBMP函数支持。
/**
* $srcFile - 图形文件
* $pixel - 尺寸大小，如：400*300
* $_quality - 图片质量，默认75
* $cut - 是否裁剪，默认1，当$cut=0的时候，将不进行裁剪
* $cache - 如果有缓存，是否直接用缓存，默认true
* 示例："< img src=\"".MiniImg('images/image.jpg','300*180',72,0)."\">"
* */
function MiniImg($srcFile, $pixel, $_quality = 75, $cut=1, $cache=true){
$_type = strtolower(substr(strrchr($srcFile,"."),1));
$pixelInfo = explode('*', $pixel);
$pathInfo = pathinfo($srcFile);
$_cut = intval($cut);
$searchFileName = preg_replace("/\.([A-Za-z0-9]+)$/isU", "_".$pixelInfo[0]."x".$pixelInfo[1]."_".$cut.".\", $pathInfo['basename']);
$miniFile = $pathInfo['dirname'].'/'.$searchFileName;
if($cache and file_exists($miniFile)) return $miniFile;
$data = GetImageSize($srcFile);
$FuncExists = 1;
switch ($data[2]) {
case 1: //gif
if(function_exists('ImageCreateFromGIF')) $_im = ImageCreateFromGIF($srcFile);
break;
case 2: //jpg
if(function_exists('imagecreatefromjpeg')) $_im = imagecreatefromjpeg($srcFile);
break;
case 3: //png
if(function_exists('ImageCreateFromPNG')) $_im = ImageCreateFromPNG($srcFile);
break;
case 6: //bmp，这里需要用到ImageCreateFromBMP
$_im = ImageCreateFromBMP($srcFile);
break;
}
if(!$_im) return $srcFile;
$sizeInfo['width'] = @imagesx($_im);
$sizeInfo['height'] = @imagesy($_im);
if(!$sizeInfo['width'] or !$sizeInfo['height']) return $srcFile;
if($sizeInfo['width'] == $pixelInfo[0] && $sizeInfo['height'] == $pixelInfo[1] ) {
return $srcFile;
}elseif($sizeInfo['width'] < $pixelInfo[0] && $sizeInfo['height'] < $pixelInfo[1] && $miniMode=='2'){
return $srcFile;
}else{
$resize_ratio = ($pixelInfo[0])/($pixelInfo[1]);
$ratio = ($sizeInfo['width'])/($sizeInfo['height']);
if($cut==1){
$newimg = imagecreatetruecolor($pixelInfo[0],$pixelInfo[1]);
if($ratio>=$resize_ratio){ //高度优先
imagecopyresampled($newimg, $_im, 0, 0, 0, 0, $pixelInfo[0],$pixelInfo[1], (($sizeInfo['height'])*$resize_ratio), $sizeInfo['height']);
$_result = ImageJpeg ($newimg,$miniFile, $_quality);
}else{ //宽度优先
imagecopyresampled($newimg, $_im, 0, 0, 0, 0, $pixelInfo[0], $pixelInfo[1], $sizeInfo['width'], (($sizeInfo['width'])/$resize_ratio));
$_result = ImageJpeg ($newimg,$miniFile, $_quality);
}
}else{ //不裁图
if($ratio>=$resize_ratio){
$newimg = imagecreatetruecolor($pixelInfo[0],($pixelInfo[0])/$ratio);
imagecopyresampled($newimg, $_im, 0, 0, 0, 0, $pixelInfo[0], ($pixelInfo[0])/$ratio, $sizeInfo['width'], $sizeInfo['height']);
$_result = ImageJpeg ($newimg,$miniFile, $_quality);
}else{
$newimg = imagecreatetruecolor(($pixelInfo[1])*$ratio,$pixelInfo[1]);
imagecopyresampled($newimg, $_im, 0, 0, 0, 0, ($pixelInfo[1])*$ratio, $pixelInfo[1], $sizeInfo['width'], $sizeInfo['height']);
$_result = ImageJpeg ($newimg,$miniFile, $_quality);
}
}
ImageDestroy($_im);
ImageDestroy($newimg);
if($_result) return $miniFile;
return $srcFile;
}
}
以下是ImageCreateFromBMP函数
ImageCreateFromBMP() – 支持BMP图片函数
/**
* ImageCreateFromBMP() - 支持BMP图片函数
* $filename - BMP图形文件
* */
function ImageCreateFromBMP( $filename ) {
// Ouverture du fichier en mode binaire
if ( ! $f1 = @fopen ($filename, "rb")) return FALSE ;
// 1 : Chargement des ent?tes FICHIER
$FILE = unpack ( "vfile_type/Vfile_size/Vreserved/Vbitmap_offset" , fread($f1 ,14));
if ( $FILE ['file_type'] != 19778 ) return FALSE ;
// 2 : Chargement des ent?tes BMP
$BMP = unpack ( 'Vheader_size/Vwidth/Vheight/vplanes/vbits_per_pixel' .
'/Vcompression/Vsize_bitmap/Vhoriz_resolution' .
'/Vvert_resolution/Vcolors_used/Vcolors_important' , fread ( $f1 , 40 ));
$BMP [ 'colors' ] = pow ( 2 , $BMP['bits_per_pixel ' ]);
if ( $BMP ['size_bitmap'] == 0 ) $BMP ['size_bitmap']=$FILE ['file_size']-$FILE ['bitmap_offset'];
$BMP ['bytes_per_pixel'] = $BMP ['bits_per_pixel'] / 8 ;
$BMP ['bytes_per_pixel2'] = ceil ( $BMP ['bytes_per_pixel']);
$BMP ['decal'] = ( $BMP ['width']*$BMP ['bytes_per_pixel'] / 4 );
$BMP ['decal'] -= floor ( $BMP ['width'] * $BMP ['bytes_per_pixel'] / 4 );
$BMP ['decal'] = 4 - ( 4 * $BMP ['decal']);
if ( $BMP ['decal'] == 4 ) $BMP ['decal'] = 0 ;
// 3 : Chargement des couleurs de la palette
$PALETTE = array ();
if ( $BMP ['colors'] < 16777216 ){
$PALETTE = unpack ( 'V' . $BMP ['colors'] , fread ( $f1 , $BMP ['colors'] * 4 ));
}
// 4 : Cr?ation de l'image
$IMG = fread ( $f1 , $BMP ['size_bitmap']);
$VIDE = chr ( 0 );
$res = imagecreatetruecolor( $BMP ['width'] , $BMP ['height']);
$P = 0 ;
$Y = $BMP ['height'] - 1 ;
while ( $Y >= 0 ){
$X = 0 ;
while ( $X < $BMP ['width']){
if ( $BMP ['bits_per_pixel'] == 24 )
$COLOR = @unpack ( "V" , substr($IMG,$P,3).$VIDE );
elseif ( $BMP['bits_per_pixel']== 16 ){
$COLOR = unpack ( "n" , substr ( $IMG , $P , 2 ));
$COLOR [1] = $PALETTE [ $COLOR [ 1 ] + 1 ];
}elseif ( $BMP['bits_per_pixel']== 8 ){
$COLOR = unpack ( "n" , $VIDE . substr ( $IMG , $P , 1 ));
$COLOR [1] = $PALETTE [ $COLOR [ 1 ] + 1 ];
}elseif ( $BMP['bits_per_pixel']== 4 ){
$COLOR = unpack ( "n" , $VIDE . substr ( $IMG , floor ( $P ) , 1 ));
if (( $P * 2 ) % 2 == 0 )
$COLOR [1] = ( $COLOR [1] >> 4 ) ;
else
$COLOR [1] = ( $COLOR [1] & 0x0F );
$COLOR [1] = $PALETTE [ $COLOR [1] + 1 ];
}elseif ( $BMP['bits_per_pixel']== 1 ){
$COLOR = unpack ( "n" , $VIDE . substr ( $IMG , floor ( $P ) , 1 ));
if (( $P * 8 ) % 8 == 0 ) $COLOR [ 1 ] = $COLOR [ 1 ] >> 7 ;
elseif (( $P * 8 ) % 8 == 1 ) $COLOR [1] = ( $COLOR [1] & 0x40 ) >> 6 ;
elseif (( $P * 8 ) % 8 == 2 ) $COLOR [1] = ( $COLOR [1] & 0x20 ) >> 5 ;
elseif (( $P * 8 ) % 8 == 3 ) $COLOR [1] = ( $COLOR [1] & 0x10 ) >> 4 ;
elseif (( $P * 8 ) % 8 == 4 ) $COLOR [1] = ( $COLOR [1] & 0x8 ) >> 3 ;
elseif (( $P * 8 ) % 8 == 5 ) $COLOR [1] = ( $COLOR [1] & 0x4 ) >> 2 ;
elseif (( $P * 8 ) % 8 == 6 ) $COLOR [1] = ( $COLOR [1] & 0x2 ) >> 1 ;
elseif (( $P * 8 ) % 8 == 7 ) $COLOR [1] = ( $COLOR [1] & 0x1 );
$COLOR [1] = $PALETTE [ $COLOR [1] + 1 ];
}else return FALSE ;
imagesetpixel( $res , $X , $Y , $COLOR [ 1 ]);
$X ++ ;
$P += $BMP['bytes_per_pixel'];
}
$Y -- ;
$P += $BMP['decal'];
}
// Fermeture du fichier
fclose ( $f1 );
return $res ;
}